The official KERNEL.SYS is loaded by BOOT.SYS when the host boots up, either during your first connection into the game world to that host, or by issuing the reboot command in-game.

The KERNEL.SYS can be completely replaced with a new binary you create yourself, however, if you change out the kernel, be sure to either use a compatible API with the official kernel, or have new tools created which use your kernel's unique API.

Currently the source code the official kernel is unavailable, however rumor has it some players have been able to successfully disassemble the kernel binary back into assembly source code.

APIs provided

JSR call

Address in memory

JSR _print

$fe00

JSR _input

$fe03

JSR _cmpstr

$fe06

JSR _memclr

$fe09

JSR _memcpy

$fe12

For some of these APIs, you will need to set some specific arguments, these are located from $fa-$fd, and a result can be read from $ff.